Card # 45-Reflection of light: When light falls on the surface of separation of two media, a part of it returns into the same medium and the remaining part of it is absorbed by the surface. If the surface is polished like a plain mirror, then a large fraction of incident light is sent back into the same medium along a definite direction, this phenomenon is called Reflection. Mirror‐ Mirror is a device which reflects the entire light incident on it. It is mainly of two types 1) Plane Mirror 2) Spherical Mirror‐ (a) Concave mirror (b) Convex mirror Reflection of light from a plane mirror‐ Laws of Reflection: (1) The Incident ray (IO ), the Reflected ray( OR ) and the normal ( NO ) at the point of incidence(O), all lie in the same plane. (2) The angle of reflection ( i ) and the angle of incidence ( r ) are equal. Image: When rays starting from a point of object suffer a change in direction due to reflection (or refraction) the reflected rays meet or appear to meet at another point, that point is called the image point of that object. Real image: Light rays after reflection or refraction actually meet at a point a real image is formed. A real image can be obtained on the screen. A real image is always inverted. Virtual image:
Light rays after reflection or refraction do not actually meet at a point, but when produced backward, the image is formed at that point is virtual, so a virtual image cannot be obtained on the screen. A virtual image is always erect.
Formation of image by plane mirror: Nature of image formed by a plane mirror: 1) Distance of object in front of the mirror = Distance of object behind the mirror 2) Size of the object = Size of the mirror Thus magnification = 1 3) Image is virtual, laterally inverted and erect; it cannot be obtained on the screen. 4) The radius of curvature of plane mirror is infinity. Its focal length is therefore Infinity.